This invention relates generally to a closure system for a container for shipping, storing and using toxic and corrosive liquid chemicals and particularly to a closure system for total sealing of ultra-high purity chemicals of the type used in manufacturing semiconductor and optical fiber devices.
It is well established that the successful manufacturing of semiconductor devices is dependent upon the use of high purity raw materials. Reliability improvements and improvements in basic physical parameters such as junction leakage, flat band voltage shift, minority carrier lifetime, etc., illustrate the necessity of maintaining a high degree of purity in raw materials. The yield of usuable components is also dependent upon raw material purity. Manufacturing of semiconductor devices is a high volume, low unit cost process. Competitive pressures result in drastic price erosion for a given semiconductor device until the high volume, low cost equilibrium state is achieved. Since the quality and device yield are highly dependent upon the purity of raw materials, the equilibrium, or profitable state, requires constant raw material purity.
The substances used in manufacturing semiconductor and optical fiber devices include phosphorus oxychloride, phosphorus trichloride, trichloroethane, tetraethyl orthosilicate, silicon tetrabromide, phosphorus tribromide, arsenic trichloride, etc. These chemicals are generally in liquid form and are hazardous to varying degrees. Therefore, they require a minimum or zero exposure to workers handling them.
In the U.S., such corrosive materials, class B poisons and the like, are subject to regulation by the Department of Transportation and other governmental agencies. Regulations, health and safety factors must be considered in shipping, storing and using these liquid materials.
In the semiconductor manufacturing industry, these chemicals are ordinarily removed from a container by passing an inert gas through the liquids. The gas becomes saturated with the vapors of the chemical by bubbling through the liquid. The gas exits the container, carrying the chemical vapors to a diffusion furnace or to a thin film reactor.
The standard container used for storing, shipping and using liquid chemicals in semiconductor and optical fiber fabrication is a bubbler produced by the assignee of the present invention and described in U.S. Pat. Nos. 4,134,514 and 4,298,037. The bubbler includes a generally cylindrical container that is partially filled with the liquid chemical and hermetically sealed to provide complete isolation of the chemical from the environment. The bubbler includes an inlet tube and an outlet tube. Each of the inlet and outlet tubes includes a quartz breakseal and an outer seal extending across the tube to prevent access to the container.
The bubbler is used by first breaking or removing the external or outer seals and connecting the inlet tube to a carrier gas supply and the outlet tube to a system to receive the chemical substance contained in the bubbler. Inlet and outlet shutoff valves are attached to the tubes, and the spaces between the inlet and outlet tubes between the respective valves and the inner breakable seals are then flushed with dry, clean inert gas to remove atmospheric moisture that may have collected there. The internal seals may then be broken.
Although the bubbler described above is satisfactory for maintaining the integrity of the ultra-high purity chemicals and protecting the environment from contamination, the bubbler is costly to manufacture, and the quartz breakseals are a considerable factor in the costs. Since at least the inner seal must be broken to remove the chemical from the bubbler container, the bubbler requires costly refurbishment for subsequent reuse.
Accordingly, there is a need in the art for a relatively simple and inexpensive bubbler closure to provide total containment of a corrosive chemical substance during storing, shipping and use. There is also a need in the art for a bubbler closure which eliminates the necessity of costly refurbishment before reuse, is simpler to manufacture and which simplifies the filling and sealing of the ultra-high purity chemical in the bubbler and facilitates safe handling of the bubbler and enclosed chemical.